Use Apache Spark to read and write Apache HBase data

Straipsnis
02/28/2024

Apache HBase is typically queried either with its low-level API (scans, gets, and puts) or with a SQL syntax using Apache Phoenix. Apache also provides the Apache Spark HBase Connector. The Connector is a convenient and efficient alternative to query and modify data stored by HBase.

Prerequisites

Two separate HDInsight clusters deployed in the same virtual network. One HBase, and one Spark with at least Spark 2.1 (HDInsight 3.6) installed. For more information, see Create Linux-based clusters in HDInsight using the Azure portal.
The URI scheme for your clusters primary storage. This scheme would be wasb:// for Azure Blob Storage, abfs:// for Azure Data Lake Storage Gen2 or adl:// for Azure Data Lake Storage Gen1. If secure transfer is enabled for Blob Storage, the URI would be wasbs://. See also, secure transfer.

Overall process

The high-level process for enabling your Spark cluster to query your HBase cluster is as follows:

Prepare some sample data in HBase.
Acquire the hbase-site.xml file from your HBase cluster configuration folder (/etc/hbase/conf), and place a copy of hbase-site.xml in your Spark 2 configuration folder (/etc/spark2/conf). (OPTIONAL: use script provided by HDInsight team to automate this process)
Run spark-shell referencing the Spark HBase Connector by its Maven coordinates in the packages option.
Define a catalog that maps the schema from Spark to HBase.
Interact with the HBase data using either the RDD or DataFrame APIs.

Prepare sample data in Apache HBase

In this step, you create and populate a table in Apache HBase that you can then query using Spark.

Use the ssh command to connect to your HBase cluster. Edit the command by replacing HBASECLUSTER with the name of your HBase cluster, and then enter the command:
```
ssh sshuser@HBASECLUSTER-ssh.azurehdinsight.net
```
Use the hbase shell command to start the HBase interactive shell. Enter the following command in your SSH connection:
```
hbase shell
```
Use the create command to create an HBase table with two-column families. Enter the following command:
```
create 'Contacts', 'Personal', 'Office'
```

Use the put command to insert values at a specified column in a specified row in a particular table. Enter the following command:

put 'Contacts', '1000', 'Personal:Name', 'John Dole'
put 'Contacts', '1000', 'Personal:Phone', '1-425-000-0001'
put 'Contacts', '1000', 'Office:Phone', '1-425-000-0002'
put 'Contacts', '1000', 'Office:Address', '1111 San Gabriel Dr.'
put 'Contacts', '8396', 'Personal:Name', 'Calvin Raji'
put 'Contacts', '8396', 'Personal:Phone', '230-555-0191'
put 'Contacts', '8396', 'Office:Phone', '230-555-0191'
put 'Contacts', '8396', 'Office:Address', '5415 San Gabriel Dr.'

Use the exit command to stop the HBase interactive shell. Enter the following command:
```
exit
```

Run scripts to set up connection between clusters

To set up the communication between clusters, follow the steps to run two scripts on your clusters. These scripts will automate the process of file copying described in 'Set up communication manually' section.

The script you run from the HBase cluster will upload hbase-site.xml and HBase IP-mapping information to the default storage attached to your Spark cluster.
The script that you run from the Spark cluster sets up two cron jobs to run two helper scripts periodically:
1. HBase cron job – download new hbase-site.xml files and HBase IP mapping from Spark default storage account to local node
2. Spark cron job – checks if a Spark scaling occurred and if cluster is secure. If so, edit /etc/hosts to include HBase IP mapping stored locally

NOTE: Before proceeding, make sure you've added the Spark cluster’s storage account to your HBase cluster as secondary storage account. Make sure you the scripts in order as indicated.

Use Script Action on your HBase cluster to apply the changes with the following considerations:

Property	Value
Bash script URI	`https://hdiconfigactions2.blob.core.windows.net/hbasesparkconnect/connector-hbase.sh`
Node type(s)	Region
Parameters	`-s SECONDARYS_STORAGE_URL -d "DOMAIN_NAME`
Persisted	yes

SECONDARYS_STORAGE_URL is the url of the Spark side default storage. Parameter Example: -s wasb://sparkcon-2020-08-03t18-17-37-853z@sparkconhdistorage.blob.core.windows.net -d "securehadooprc"

Use Script Action on your Spark cluster to apply the changes with the following considerations:

Property	Value
Bash script URI	`https://hdiconfigactions2.blob.core.windows.net/hbasesparkconnect/connector-spark.sh`
Node type(s)	Head, Worker, Zookeeper
Parameters	`-s "SPARK-CRON-SCHEDULE" (optional) -h "HBASE-CRON-SCHEDULE" (optional) -d "DOMAIN_NAME" (mandatory)`
Persisted	yes

You can specify how often you want this cluster to automatically check if update. Default: -s “*/1 * * * *” -h 0 (In this example, the Spark cron runs every minute, while the HBase cron doesn't run)
Since HBase cron isn't set up by default, you need to rerun this script when perform scaling to your HBase cluster. If your HBase cluster scales often, you may choose to set up HBase cron job automatically. For example: -s '*/1 * * * *' -h '*/30 * * * *' -d "securehadooprc" configures the script to perform checks every 30 minutes. This will run HBase cron schedule periodically to automate downloading of new HBase information on the common storage account to local node.

Note

These scripts works only on HDI 5.0 and HDI 5.1 clusters.

Set up communication manually (Optional, if provided script in above step fails)

NOTE: These steps need to perform every time one of the clusters undergoes a scaling activity.

Copy the hbase-site.xml from local storage to the root of your Spark cluster's default storage. Edit the command to reflect your configuration. Then, from your open SSH session to the HBase cluster, enter the command:

Syntax value	New value
URI scheme	Modify to reflect your storage. The syntax is for blob storage with secure transfer enabled.
`SPARK_STORAGE_CONTAINER`	Replace with the default storage container name used for the Spark cluster.
`SPARK_STORAGE_ACCOUNT`	Replace with the default storage account name used for the Spark cluster.

hdfs dfs -copyFromLocal /etc/hbase/conf/hbase-site.xml wasbs://SPARK_STORAGE_CONTAINER@SPARK_STORAGE_ACCOUNT.blob.core.windows.net/

Then exit your ssh connection to your HBase cluster.
```
exit
```
Connect to the head node of your Spark cluster using SSH. Edit the command by replacing SPARKCLUSTER with the name of your Spark cluster, and then enter the command:
```
ssh sshuser@SPARKCLUSTER-ssh.azurehdinsight.net
```
Enter the command to copy hbase-site.xml from your Spark cluster's default storage to the Spark 2 configuration folder on the cluster's local storage:
```
sudo hdfs dfs -copyToLocal /hbase-site.xml /etc/spark2/conf
```

Run Spark Shell referencing the Spark HBase Connector

After you complete the preceding step, you should be able to run Spark shell, referencing the appropriate version of Spark HBase Connector.

As an example, the following table lists two versions and the corresponding commands the HDInsight team currently uses. You can use the same versions for your clusters if the versions of HBase and Spark are same as indicated in the table.

In your open SSH session to the Spark cluster, enter the following command to start a Spark shell:

Spark version	HDI HBase version	SHC version	Command
2.1	HDI 3.6 (HBase 1.1)	1.1.1-2.1-s_2.11	`spark-shell --packages com.hortonworks:shc-core:1.1.1-2.1-s_2.11 --repositories https://repo.hortonworks.com/content/groups/public/`

Keep this Spark shell instance open and continue to Define a catalog and query. If you don't find the jars that correspond to your versions in the SHC Core repository, continue reading.

For subsequent combinations of Spark and HBase versions, these artifacts are no longer published at above repo. You can build the jars directly from the spark-hbase-connector GitHub branch. For example, if you're running with Spark 2.4 and HBase 2.1, complete these steps:

Clone the repo:

git clone https://github.com/hortonworks-spark/shc

Go to branch-2.4:
```
git checkout branch-2.4
```
Build from the branch (creates a .jar file):
```
mvn clean package -DskipTests
```
Run the following command (be sure to change the .jar name that corresponds to the .jar file you built):
```
spark-shell --jars <path to your jar>,/usr/hdp/current/hbase-client/lib/shaded-clients/*
```
Keep this Spark shell instance open and continue to the next section.

Define a catalog and query

In this step, you define a catalog object that maps the schema from Apache Spark to Apache HBase.

In your open Spark Shell, enter the following import statements:

import org.apache.spark.sql.{SQLContext, _}
import org.apache.spark.sql.execution.datasources.hbase._
import org.apache.spark.{SparkConf, SparkContext}
import spark.sqlContext.implicits._

Enter the command below to define a catalog for the Contacts table you created in HBase:

def catalog = s"""{
    |"table":{"namespace":"default", "name":"Contacts"},
    |"rowkey":"key",
    |"columns":{
    |"rowkey":{"cf":"rowkey", "col":"key", "type":"string"},
    |"officeAddress":{"cf":"Office", "col":"Address", "type":"string"},
    |"officePhone":{"cf":"Office", "col":"Phone", "type":"string"},
    |"personalName":{"cf":"Personal", "col":"Name", "type":"string"},
    |"personalPhone":{"cf":"Personal", "col":"Phone", "type":"string"}
    |}
|}""".stripMargin

The code:

Defines a catalog schema for the HBase table named Contacts.
Identifies the rowkey as key, and map the column names used in Spark to the column family, column name, and column type as used in HBase.
Defines the rowkey in detail as a named column (rowkey), which has a specific column family cf of rowkey.

Enter the command to define a method that provides a DataFrame around your Contacts table in HBase:

def withCatalog(cat: String): DataFrame = {
    spark.sqlContext
    .read
    .options(Map(HBaseTableCatalog.tableCatalog->cat))
    .format("org.apache.spark.sql.execution.datasources.hbase")
    .load()
 }

Create an instance of the DataFrame:
```
val df = withCatalog(catalog)
```

Query the DataFrame:

df.show()

You should see two rows of data:

+------+--------------------+--------------+-------------+--------------+
|rowkey|       officeAddress|   officePhone| personalName| personalPhone|
+------+--------------------+--------------+-------------+--------------+
|  1000|1111 San Gabriel Dr.|1-425-000-0002|    John Dole|1-425-000-0001|
|  8396|5415 San Gabriel Dr.|  230-555-0191|  Calvin Raji|  230-555-0191|
+------+--------------------+--------------+-------------+--------------+

Issue a SQL query against the contacts table:

spark.sqlContext.sql("select personalName, officeAddress from contacts").show

You should see results like these:

+-------------+--------------------+
| personalName|       officeAddress|
+-------------+--------------------+
|    John Dole|1111 San Gabriel Dr.|
|  Calvin Raji|5415 San Gabriel Dr.|
+-------------+--------------------+

Insert new data

To insert a new Contact record, define a ContactRecord class:

case class ContactRecord(
    rowkey: String,
    officeAddress: String,
    officePhone: String,
    personalName: String,
    personalPhone: String
    )

Create an instance of ContactRecord and put it in an array:

val newContact = ContactRecord("16891", "40 Ellis St.", "674-555-0110", "John Jackson","230-555-0194")

var newData = new Array[ContactRecord](1)
newData(0) = newContact

Save the array of new data to HBase:

sc.parallelize(newData).toDF.write.options(Map(HBaseTableCatalog.tableCatalog -> catalog, HBaseTableCatalog.newTable -> "5")).format("org.apache.spark.sql.execution.datasources.hbase").save()

Examine the results:

df.show()

You should see output like this:

+------+--------------------+--------------+------------+--------------+
|rowkey|       officeAddress|   officePhone|personalName| personalPhone|
+------+--------------------+--------------+------------+--------------+
|  1000|1111 San Gabriel Dr.|1-425-000-0002|   John Dole|1-425-000-0001|
| 16891|        40 Ellis St.|  674-555-0110|John Jackson|  230-555-0194|
|  8396|5415 San Gabriel Dr.|  230-555-0191| Calvin Raji|  230-555-0191|
+------+--------------------+--------------+------------+--------------+

Close the spark shell by entering the following command:
```
:q
```

Next steps

Apache Spark HBase Connector

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